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Eur. J. Mineral., 32, 67–75, 2020 https://doi.org/10.5194/ejm-32-67-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.

Raman spectroscopic identiﬁcation of cookeite in the crystal-rich inclusions in spodumene from the Jiajika lithium pegmatite deposit, China, and its geological implications

Xin Ding1, Jiankang Li2, I-Ming Chou3, Zhenyu Chen2, and Shenghu Li4 1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing 100083, China 2MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China 3CAS Key Laboratory of Experimental Study Under Deep-sea Extreme Conditions, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China 4Shandong Institute of Geological Sciences, Ji’nan 250013, China Correspondence: Jiankang Li ([email protected])

Received: 1 January 2019 – Accepted: 18 September 2019 – Published: 16 January 2020

Abstract. Cookeite usually occurs as a late alteration product in lithium–cesium–tantalum-type granitic pegmatite. Consequently, cookeite-bearing crystal-rich inclusions (CIs) in pegmatite are considered to be of secondary origin, which constrains our understanding of pegmatite formation. Thus far, no reported cookeite has produced a distinct Raman spectrum. However, the CIs hosted in spodumene in the Jiajika pegmatite deposit, China, contain a cookeite-like hydrous lithium–aluminum–silicate phase, yielding a distinct Raman spectrum. In electron microprobe analysis, focused ion beam scanning electron microscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the average composition of this hydrous phase was determined as Li1.005(Al3.997Fe0.018)(Si3.086Al0.914)O10.076OH7.902F0.098, close to the International Mineralogical Association (IMA) formula of cookeite, (Al, Li)3Al2(Si, Al)4O10(OH)8. The distinct Raman peaks at 98, 167, 219, 266, 342, 382, 457, 592, 710, and 3640 cm−1 were consistent with those of natural cookeite recrystallized in a hydrothermal diamond-anvil cell. The peaks were ascribed to the crystallization of cookeite from the liquid trapped in the closed space during the spodumene crystallization, which occurred at relatively high temperature and pressure without incorporating the minor elements commonly present during alteration processes. These minor elements often obscure the Raman signals, primarily by fluorescence effects. This type of cookeite in CIs with distinct Raman signals is unusual and can indicate whether the cookeite crystallized from fluid trapped within the closed space of a primary inclusion. In such a case, the fluid can be considered a flux-rich hydrous melt in pegmatite formation models.

1 Introduction 1970; Heinrich, 1975; London and Burt, 1982; Bobos et al., 2007; Novák et al., 2015). Cookeite is occasionally found Cookeite is an uncommon member of the chlorite group, in hydrothermal veins or hydrothermally altered sedimen- tary rocks (Vidal and Goffé, 1991). It also occurs in crystal- with the IMA formula LiAl4(Si3Al)O10(OH)8 (Anthony et al., 1995). Most cookeite is a late hydrothermal alteration rich inclusions (CIs), which characterize the ﬂuid inclusions product of spodumene, petalite, and other Li-rich minerals, in granitic pegmatites (Roedder, 1992). Because cookeite is which form in granite pegmatites at low temperatures (Cerný,ˇ conventionally thought to have formed in the late-stage al-

Published by Copernicus Publications on behalf of the European mineralogical societies DMG, SEM, SIMP & SFMC. 68 X. Ding et al.: Raman spectrum of cookeite teration processes, its presence in CIs implies a secondary origin of the CIs (Anderson et al., 2001; Anderson and Mac- carron, 2011; Anderson, 2013). Despite its common occurrence, no natural cookeite, including CI-enclosed cookeites in pegmatite environments, is known to produce distinct Ra- man signals. Consequently, no characteristic Raman spectrum of cookeite has been reported. In the database of Ra- man spectra, X-ray diffraction, and chemical data (RRUFF), the Raman spectra of cookeite are very noisy, with no distinct peaks (Downs, 2006). Therefore, cookeite has been identified mainly by analyzing its composition or by semiquantitative X-ray spectroscopy (London, 1986; Anderson and Maccar- ron, 2011). However, the Jiajika pegmatite-type lithium deposit in western Sichuan, China, contains a cookeite-like hydrous solid phase within spodumene-hosted CIs, which yields a distinct Raman spectrum (Fig. 5 in Li and Chou, 2016). In the present study, this hydrous solid phase is confirmed as being cookeite by further analyses, including with an electron Figure 1. Photomicrographs of spodumene-hosted crystal-rich in- microprobe (EMP), focused ion beam scanning electron mi- clusions (CIs) in the Jiajika deposit, showing one fluid inclusion croscope (FIB-SEM), and time-of-flight secondary ion mass assembly (FIA) of CIs with a uniform composition and the crys- spectrometer (ToF-SIMS); its Raman signals are compared tal/fluid proportion. Crt – cristobalite; Spd – spodumene; Zab – with those of a natural cookeite recrystallized in a hydrother- zabuyelite; Cal – calcite, Qz – quartz; Ck – cookeite. mal diamond-anvil cell (HDAC). Given the unusual Raman feature of the cookeite in the CIs from the Jiajika pegmatite, Mn)PO ). The spodumene crystals are white or off-white we infer an origin different from those of secondary CIs (An- 4 euhedral plates 5–10 cm in length and 1–5 cm in width and derson et al., 2001; Anderson and Maccarron, 2011; Ander- are clearly in contact with quartz and albite crystals (Li and son, 2013). The cookeite might have formed from fluid origi- Chou, 2016). The late alteration is relatively weak in the nally trapped during the crystallization of spodumene. There- spodumene pegmatite, and occasionally spodumene was re- fore, this fluid can be considered to be a primary flux-rich placed by albite in myrmekitic texture at the contact face with hydrous melt in pegmatite formation models (London, 1999, microcline. Currently, cookeite crystals, formed through late 2008, 2018; Thomas et al., 2000, 2009, 2011a, b). In this hydrothermal alteration of spodumene at low temperature, paper, we suggest that cookeite in CIs with distinct Raman were not observed in the pegmatite dikes. signals is a viable indicator of the primary nature of CIs in In the spodumene pegmatite in the Jiajika deposit, the CIs pegmatite. of the spodumene often contain a hydrous solid phase that has been identified and imaged with Raman spectroscopy (Figs. 1, 2; Li and Chou, 2016). Electron microprobe (EMP) 2 Features of cookeite-like phases within the analyses suggest a cookeite composition of this phase (Li and crystal-rich inclusions in the Jiajika pegmatite Chou, 2016). The CIs, which often occur as isolated indi- deposit viduals or in-fluid inclusion assemblages (FIAs) with similar composition and crystal/fluid proportion, are considered to The Jiajika granitic pegmatite in western Sichuan, China, is be primary in origin (Fig. 1). The exceptions are FIAs of CIs the largest lithium deposit in Asia (Li et al., 2013a). In this that are cross-cut by late stage CO –H O–NaCl and aqueous deposit, the pegmatite dikes radiate horizontally and verti- 2 2 fluid inclusions (Li and Chou, 2016, 2017). The primary CIs cally around the two-mica granite intrusion. With increas- are 20–100 µm long and 10–20 µm wide and have a subhedral ing distance from the granite, the mineralogy of pegmatite to euhedral negative spodumene crystal shape. Within the dikes change from microcline pegmatite, to microcline-albite CIs, the cookeite-like phase is commonly accompanied by pegmatite, albite pegmatite, spodumene pegmatite, and lep- semi-euhedral crystals of zabuyelite, cristobalite, and quartz idolite (muscovite) pegmatite. The two-mica granite and (Fig. 2; Li and Chou, 2016). It coexists with a CO phase, pegmatites are hosted in schists formed by metamorphic 2 and occasionally coexists with an aqueous phase (Figs. 1 overprint of early Triassic mudstones and sandstones (Li and 2). In CI heating experiments, the cookeite-like phase, et al., 2007). The spodumene pegmatite dikes are the main zabuyelite, cristobalite, and quartz dissolve and melt at 400– lithium ore bodies; they are mainly composed of spodumene, 600 ◦C, and the CIs are homogenized into a carbonate-rich quartz, albite, muscovite, and a few rare metal minerals aqueous fluid at 500–700 ◦C (Li and Chou, 2017). of columbite, beryl, tantalite, thorite, and sicklerite ((Li,

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mounted on a TESCAN LYRA instrument platform (TOFW- ERK AG, CNNC Beijing Research Institute of Uranium Ge- ology). In this analysis, the ion beam energy and current were set to 15 keV and 200 pA, respectively. The staying time and milling depth on the crystal surface were 10 µs and ∼ 0.2 µm, respectively, over an area of approximately (10 × 10) µm2. To prove that the hydrous solid phase in CIs is indeed cookeite, we recrystallized a natural cookeite sample from Minas Gerais pegmatite, Brazil (Catalogue No. 115846 00, National Museum of Natural History, Smithsonian Institu- tion, USA), in a hydrothermal diamond-anvil cell (HDAC, type HDAC-VT; Li et al., 2016). The cookeite sample contained 46.63 wt % Al2O3, 35.77 wt % SiO2, 0.62 wt % F, 0.24 wt % MnO, 0.09 wt % SnO, 0.08 wt % SrO, 0.03 wt % Cs2O, 0.03 wt % Pb, 0.02 wt % K2O, 0.01 wt % Cl, which were analyzed with EMP at the conditions described above. Following Li et al. (2013b), the preheated cookeite sample and pure water were sealed together with an air bubble in the HDAC sample chamber. The sample chamber is a hole Figure 2. Crystal-rich inclusions (CIs) hosted in spodumene from (of diameter 0.5 mm) at the center of a Re gasket (of diam- the Jiajika deposit. Crt – cristobalite, Spd – spodumene, Zab – eter and thickness 3.0 and 0.125 mm, respectively), sealed zabuyelite; Cal – calcite, Qz – quartz; Ck – cookeite. (d) Raman by compressing the gasket with two parallel diamond-anvil map of the CI shown in (c). The length of the scale bar is 10 µm. faces (1.0 mm diameter). During heating, the sample temperatures were controlled and measured by a temperature con- troller (PES 1300, PES Enterprise Inc., USA). After care- 3 Analytical methods of cookeite fully determining the temperature at which the vapor bub- ◦ −1 ble disappeared (ThDC), the sample was heated at 5 C min The hydrous solid phase within the spodumene-hosted CIs until the cookeite began to dissolve and melt. The heating was analyzed by Raman spectroscopy (Horiba LabRam rate was then reduced by 1 ◦C min−1 until approximately HR800 Raman spectrometer, Horiba Trading Co., Ltd., Bei- 40 vol % of the cookeite had dissolved and melted. Subse- jing Branch, China). To minimize ﬂuorescence, the excita- quently, the sample chamber was cooled at 1 ◦C min−1 to ap- tion beam wavelength was set to 633 nm. The power on the proximately 200 ◦C, when the cookeite recrystallized around sample surface was 4.1 mW. The spectrometer was calibrated the remaining cookeite residue. During the heating and cool- with silica to an accuracy of ±0.2 cm−1. Two accumula- ing processes, the pressures within the HDAC chamber were tions of the unpolarized spectrum were collected for 120 s calculated from the bulk H2O densities obtained at ThDC us- for each spectral window through a 100× Olympus objec- ing the equation of state of H2O (Wagner and Pruss, 2002). tive lens (NA = 0.90). Under these conditions, one CI con- Finally, the recrystallized cookeite was removed from the taining the hydrous solid phase was mapped to an x–y res- HDAC chamber and analyzed by using a JY Horiba LabRam olution of 1 µm, with a spectrum-collecting time of 10 s per HR800 Raman spectrometer with the spectrum-collecting spot (Fig. 2d). time of 120 s with two accumulations. After polishing the sample wafer until the hydrous solid phase in the CIs was exposed to air, the sample was analyzed using a JXA-8230 EMP at the Institute of Mineral Resources, 4 Analytical results Chinese Academy of Geological Sciences, in wavelength- dispersive mode. Operating conditions for analyses were as As shown in Figs. 3b and 4 (see also Fig. 5 of Li and Chou, follows: an accelerating voltage of 15 kV, a beam current of 2016), the Raman spectra of the hydrous solid phase in the 10 nA, and a beam diameter of 10 µm was used for cookeite. CIs show clear and distinct peaks at 98, 167, 219, 266, and The following standards and X-ray lines were used, Kα 3640 cm−1. The Raman spectrum of the cookeite recrys- lines: Si, Na – Jadeite; Al – kyanite, Ca – wollastonite; K, tallized in the HDAC chamber exhibited the same peaks, F – phengite; Cr-Cr2O3; Mg – olivine; Fe – hematite; Mn – along with less-evident peaks near 342, 382, 457, 592, and spessartine; and Ti – rutile. The raw data were reduced using 710 cm−1 (Fig. 3c), without the noise of natural cookeite as the ZAF correction procedure. shown in Fig. 3d. This spectrum is not obscured by the strong The composition of the exposed hydrous solid phase was Raman peaks of spodumene that hosts the CIs (Fig. 3a). then analyzed by a FIB-SEM combined with ToF-SIMS Therefore, the Raman signal of the hydrous solid phase in based on a gallium ion source. The ToF-SIMS analyzer was CIs was distinct and matched that of recrystallized cookeite. www.eur-j-mineral.net/32/67/2020/ Eur. J. Mineral., 32, 67–75, 2020 70 X. Ding et al.: Raman spectrum of cookeite

Table 1. Compositions of representative hydrous solid phases in the CIs from the Jiajika pegmatite analyzed by EMP and calculated using the chemical formula of cookeite.

Numbers of analyzed samples Average JPC-1 JPC-2 JPC-3 JPC-4 value Composition (wt %) JPC-1 JPC-2 JPC-3 JPC-4 Average

SiO2 34.45 35.36 35.96 36.27 35.51 Al2O3 49.01 48.20 47.31 47.31 47.96 Fe2O3 0.34 0.27 0.26 0.24 0.28 F 0.36 0.21 0.37 0.49 0.36 ∗ H2O 13.01 13.18 13.00 12.93 13.03 Li2O 2.84 2.78 3.12 2.76 2.87 O=F, Cl 0.15 0.09 0.15 0.21 0.15 Total 99.85 99.91 99.85 99.79 99.85 APFU 4+ Figure 3. Raman spectra of (a) inclusion-free spodumene, (b) a Si 2.998 3.067 3.123 3.154 3.086 iv hydrous solid phase in the spodumene-hosting crystal-rich inclu- Al 1.002 0.933 0.877 0.846 0.914 vi sions, and (c) recrystallized cookeite in the HDAC sample cham- Al 4.026 3.994 3.966 4.004 3.997 + ber. (d) Natural cookeite before crystallization experiments from the Fe3 0.022 0.018 0.017 0.016 0.018 + Minas Gerais pegmatite, Brazil, which bears high ﬂuorescence even Li 0.994 0.970 1.090 0.965 1.005 − when collected for 1 s with an excitation beam of 633 nm wave- OH 7.901 7.942 7.898 7.865 7.902 length through a 100× Olympus objective lens (NA = 0.90). The F 0.099 0.058 0.102 0.135 0.098 characteristic Raman peaks are marked. Total 17.977 17.983 17.987 17.965 17.978

When calculating the contents of Li2O, H2O, and the atoms per formula unit (APFU) in the hydrous solid phase (cookeite), we assumed that cookeite (chemical formula LiAl4(Si3Al)O10(OH)8) contains 18 oxygen atoms and (OH+F+Cl) = 8 ∗ per unit cell. H2O was calculated assuming (OH+F+Cl) = 8 APFU. All Fe in the solid phase was considered Fe3+.

cookeite-like phases, together with bipyramidal quartz, were strictly confined within the CI (Fig. 5a). The crystals in the SEM images taken at the ion beam energy of 5 keV appeared as 0.2–2.0 µm scales or as spherulites with diameters of 0.1– 0.2 µm (Fig. 5b). The ToF-SIMS analysis confirmed that be- sides silica and aluminum, the crystals contain rather high contents of lithium (Fig. S1 in the Supplement). Figure 4. Raman spectrum of the hydrous solid phase cookeite in In the dissolution and melting experiment of cookeite, a spodumene-hosted crystal-rich inclusion in the high wave num- the vapor-bubble-disappearing temperature (ThDC) within the −1 ◦ ber region, showing the characteristic peak near 3640 cm in a HDAC chamber was 316 C, indicating an H2O bulk density hydrous sample. of 0.67681 g cm−3 in the chamber (Wagner and Pruss, 2002). Obvious dissolution and melting of the natural cookeite began at approximately 520 ◦C and 206 MPa, and the main part The average compositions of four hydrous solid crystals was completely dissolved and melted at 620 ◦C and 301 MPa in the CIs, determined in the EMP analysis, were 47.96 wt % (Fig. 6), leaving a lot of residue. Some of this residue re- ◦ Al2O3, 35.51 wt % SiO2, and 15.90 wt % undetermined mass mained present even at 820 C and 486 MPa. In the recrys- (Table 1). In SEM observations, the hydrous solid phase is tallization experiment of cookeite, the ThDC in the HDAC ◦ in direct contact with the spodumene host, with no evidence chamber was 261 C (corresponding to an H2O density of of reaction or intergrowth with spodumene or other minerals. 0.78205 g cm−3). The natural cookeite began obviously dis- These findings are consistent with the Raman mapping result solving and melting at approximately 500 ◦C and 316 MPa, (Fig. 2d). In one CI with perfect crystal shape of spodumene, leaving residue behind the melting front (Fig. 7). Subse-

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5 Discussion

5.1 Raman spectra of cookeite within the CIs of the Jiajika pegmatite

In SEM images, the cookeite-like hydrous solid phase appeared as fine scales or spherulites (Fig. 5), consistent with the shape of cookeite described in Anthony et al. (2001). The hydrous solid phase contained 15.90 wt % undetermined mass (Table 1); according to the ToF-SIMS analysis (Fig. S1), part of the undetermined mass was lithium, and the Raman spectrum peak at 3640 cm−1 (Fig. 4) inferred an H2O content exceeding 10 wt % in the hydrous solid phase, as estimated using the method of Thomas (2000). The analyzed composition (Table 1) approaches the ideal composition of cookeite (47.96 wt % Al2O3, 35.51 wt % SiO2, 2.87 wt % Li2O, and 13.03 wt % H2O). Based on the analyzed composition, the chemical formula of the hydrous crystal was calculated as Li1.005 (Al3.997Fe0.018)(Si3.086Al0.914)O10.076OH7.902F0.098, being consistent with ideal empirical formula LiAl4(Si3Al)O10(OH)8 of cookeite (Anthony et al., 1995). It is purer than cookeite formed as a late hydrothermal alteration product of lithium-bearing minerals in pegmatite. For example, the cookeite from Minas Gerais pegmatite, Brazil, that incorporated 0.62 wt % F, 0.24 wt % MnO, 0.09 wt % SnO, 0.08 wt % SrO, 0.03 wt % Cs2O, 0.03 wt % Pb, 0.02 wt % K2O, 0.01 wt % Cl, and cookeite from the Dolní Bory-Hateˇ pegmatite in Czechia incorporated with Fe (Fetot ≤ 0.08 apfu), Mg (≤ 0.07 apfu), and K (≤ 0.15 apfu) (Novák et al., 2015). In contrast, cookeite crystals from the Kalbinsky Range pegmatite and the Djalair pegmatite in Russia bear the chemical formulas of + P 2 P (Li1.11Na0.02K0.01) =1:14(Al3.89Fe0.05Ca0.04Mg0.03) =4.01 (Si2.95Al1.05)P=4.00O10(OH)8 and + + 3 2 P 0.62 P Li0.7(Al3.96Fe0.09Fe0.04) =4.09(Si3.38Al ) =4.00O10.35 Figure 5. Two SEM images of cookeite crystals in one exposed (OH)7.65, respectively (Anthony et al., 1995). crystal-rich inclusion hosted in spodumene from the Jiajika peg- The above analysis and calculations confirm that the CI- matite. The SEM analysis conditions are shown, and the marked hosted hydrous crystal in the Jiajika pegmatite is cookeite. lengths are the entire scale bars. Spd – spodumene; Ck – cookeite; Furthermore, because the distinct Raman peaks of this hy- Qtz – quartz. drous solid phase were consistent with those of natural cookeite recrystallized in the HDAC chamber (Fig. 3), we quently, cooling was started at 565 ◦C and 402 MPa, when conclude that cookeite yields characteristic Raman peaks at −1 approximately 40 vol % of the cookeite had dissolved and 98, 167, 219, 266, 342, 382, 457, 592, 710, and 3640 cm melted. During the cooling process, the cookeite recrystal- (Figs. 3 and 4). lized into fine grains (Fig. 7). After cooling to room temperature (25 ◦C), a few recrystallized cookeite crystals with high 5.2 Formation mechanism of cookeite with distinct transparency and low fluorescence produced distinct Raman Raman spectra signals with peaks at 98, 167, 219, 266, 342, 382, 457, 592, −1 and 710 cm (Fig. 3c). Note that a peak of recrystallized The cookeite in the spodumene-hosted CIs in Tanco peg- −1 cookeite near 3640 cm , similar to that shown in Fig. 4, was matite (e.g., Anderson, 2013) usually coexists with quartz observed. and was proposed as forming during or after the incursion of late aqueous fluid along cleaved or fractured spodumene. The expected formation mechanism is an alteration reaction www.eur-j-mineral.net/32/67/2020/ Eur. J. Mineral., 32, 67–75, 2020 72 X. Ding et al.: Raman spectrum of cookeite

Figure 6. Images of the HDAC sample chamber during the cookeite dissolution and melting experiment: (a) natural cookeite surrounded by pure water at 12 MPa and 317 ◦C; (b) cookeite dissolving in water at 252 MPa and heated to 568 ◦C at 5 ◦C min−1; (c) cookeite dissolving and melting at 282 MPa and 600 ◦C (heated at 1 ◦C min−1), showing the cookeite melting front; and (d) cookeite residue after dissolution of the main part in water at 301 MPa and 620 ◦C (heated at 1 ◦C min−1). This residue remained even at 486 MPa and 820 ◦C. Pressures were −3 calculated for a bulk H2O density of 0.67681 g cm .

of spodumene + H2O → cookeite + quartz (Anderson et al., features indicate the CIs in the Jiajika pegmatite were pri- 2001; Anderson and Maccarron, 2011). mary in origin and were trapped during spodumene crys- However, many features of the CIs in the Jiajika pegmatite tallization, excluding cookeite formation through an alter- indicate these CIs to be primary in origin without incursion ation reaction of spodumene during the incursion of late fluid of late fluid (Li and Chou, 2016, 2017). The CIs in the Jiajika along cleaved or fractured spodumene, as suggested by An- pegmatite usually have a crystal shape of spodumene (e.g., derson and Maccarron (2011). Additionally, the clean and the CI in Fig. 5a), indicating the CIs were trapped during spo- straight contact face between cookeite and its spodumene dumene growth. And, in the CI with a perfect shape of spo- host excludes cookeite formation through an alteration reac- dumene shown in Fig. 5a, cookeite and bipyramidal quartz tion between the trapped aqueous fluid and spodumene (the are strictly confined within the CI, implying that cookeite and hosting mineral) (Figs. 2, 5). In the CI homogenization ex- quartz crystallized from the entrapped fluid in the CI. Fur- periments, the cookeite with cristobalite melted in the 400– ◦ thermore, within the CIs in the Jiajika deposit, SiO2 is more 600 C range, consistent with the cookeite stability field re- frequently crystallized as cristobalite (Figs. 1 and 2), show- ported by Vidal and Goffé (1991) and with the temperature ing different mineral assemblages to the above alteration re- range of pegmatite crystallization (London, 2008). There- action of spodumene. We consider that when zabuyelite or fore, cookeite might directly crystallize at relatively high P - calcite crystallized at about 500–600 ◦C in the closed space T conditions from the fluid entrapped in the closed space of of the CIs (Ding et al., 2016), the rapid pressure decrease CIs. The cookeite crystallization process in the closed space in the CIs induced cristobalite rather than quartz crystalliza- of CIs would consume the H2O within the CIs, leaving a tion in the 400–600 ◦C range (Li and Chou, 2016). These small amount of aqueous fluid or no aqueous fluid at all co-

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Figure 7. Images of the HDAC sample chamber during the cookeite recrystallization experiment: (a) natural cookeite surrounded by pure ◦ −3 ◦ H2O at 260 C and 4.7 MPa (bulk H2O density = 0.78205 g cm ; vapor bubble disappears at 261 C); (b) cookeite dissolving in water at 560 ◦C and 393 MPa (∼ 40 % cookeite (by volume) has melted, leaving residue behind the melting front); (c) the recrystallized cookeite at 200 ◦C and 1.6 MPa (vapor bubble appears during cooling); and (d) recrystallized cookeite (enlargement of the area enclosed in the rectangle in c is highly transparent and provides distinct Raman signals; see Fig. 3c). existing with the cookeite, as shown in Figs. 1 and 2. It could rities usually produce Raman spectrum with high fluores- also be the reason that the shapes of cookeite showing scales cence, as shown Fig. 3d and in the RRUFF Raman database or spherulites within CIs in the Jiajika pegmatite were differ- (Downs, 2006); as a result, no distinct Raman spectrum of ent from shapes of secondary cookeite as foliations or sheets cookeite were ever reported (Anderson and Mccarron, 2011). described by Anderson and Mccarron (2011) and Novák et On the other hand, the cookeite with low fluorescence crys- al. (2015). tallized in the closed space of CIs in the Jiajika pegmatite In contrast to the CI-hosted cookeite in the Jiajika peg- is purer than the secondary cookeite, as shown in Table 1. matite, the cookeite formed in a relatively open system The high purities are also proven by the phenomenon that through the alteration reaction. It could cause cookeite to no residue were observed after total melting of cookeite and be highly inhomogeneous (Gunter, 2018), as the loose crys- other daughter minerals in the CIs of spodumene from the tal lattice of cookeite easily absorbs many components, Jiajika pegmatite in the total homogenization experiments such as Na, Ca, Mg, K, Fe, P, and F (Cerný,ˇ 1970). For conducted by Li and Chou (2017). Furthermore, the natural example, the natural cookeite sample from Minas Gerais cookeite recrystallized in the sealed HDAC sample chamber pegmatite, Brazil, contained 0.62 wt % F, 0.24 wt % MnO, yielded distinct Raman signals, which resembled those col- 0.09 wt % SnO, 0.08 wt % SrO, 0.03 wt % Cs2O, 0.03 wt % lected from the hydrous solid phase of spodumene-hosting Pb, 0.02 wt % K2O, and 0.01 wt % Cl. As a result, residue CIs in Jiajika pegmatite. Therefore, the purities of cookeite of natural cookeite remained in the HDAC during the melt- crystallized at relatively high P -T conditions in a closed ing and recrystallization experiments (see Figs. 6 and 7). space (e.g., CIs) could be the reason of cookeite exhibit- Correspondingly, the secondary cookeite with high impu- ing low fluorescence. Therefore, if a cookeite sample ex- www.eur-j-mineral.net/32/67/2020/ Eur. J. Mineral., 32, 67–75, 2020 74 X. Ding et al.: Raman spectrum of cookeite hibits distinct Raman signals, it probably formed in a closed Competing interests. The authors declare that they have no conflict space at relatively high P -T conditions. It indicates that of interest. the cookeite-bearing CIs in the spodumene from the Jia- jika lithium pegmatite deposit are primary inclusions con- taining trapped a pegmatite-crystallization medium, such as Acknowledgements. We would like to thank two anonymous re- boundary-layer liquid (London, 2018) or hydrous-silicate (B- viewers for their constructive reviews. The National Museum of type) melt (Thomas and Davidson, 2016). This conjecture Natural History of the Smithsonian Institution supplied the natural supports our previous study, in which we inferred a primary cookeite sample from Minas Gerais pegmatite, Brazil. Raman analyses were performed at Horiba (China) Trading Co., Ltd., Beijing nature of these CIs from the presence of cristobalite within Branch. them (Li and Chou, 2016).

6 Conclusions Financial support. This research has been supported by the National Key Research and Development Program In this paper, we reported a type of cookeite hosted in CIs in (2019YFC0605203), the National Natural Science Foundation the spodumene of the Jiajika pegmatite, which yields distinct of China (grant no. 41872096), the Chinese National Non-profit Institute Research Grant of CAGS (grant no. JYYWF201814), the Raman peaks at 98, 167, 219, 266, 342, 382, 457, 592, 710, −1 Knowledge Innovation Program (grant no. SIDSSE-201302), the and 3640 cm . Raman spectroscopy has many advantages, Hadal-trench Research Program (grant no. XDB06060100), and it is non-osculatory and nondestructive and has a high sen- the Key Frontier Science Program, Chinese Academy of Sciences sitivity, short examination time, small sample size, and non- (grant no. QYZDY-SSW-DQC008). preparative sample (Chou and Wang, 2017). Therefore, our reported Raman spectrum of cookeite makes it possible to use this advantageous tool for identifying cookeite that likely Review statement. This paper was edited by Sergey Krivovichev. formed in enclosed spaces (i.e., which yields distinct Raman signals). Crystallization within the closed space at relatively high References P -T conditions might explain the high purity and distinct Raman signals of the cookeite derived from the Jiajika peg- Anderson, A. J.: Are silicate-rich inclusions in spodumene crystal- matite. As a result, this type of cookeite is unusual and pro- lized aliquots of boundary layer melt?, Geofluids, 13, 460–466, vides an indicator of cookeite crystallized in the closed space 2013. of a primary inclusion (e.g., CI). By recognizing the primary Anderson, A. J. and Maccarron, T.: Three-dimensional textural and nature of the CIs in the spodumene from the Jiajika peg- chemical characterization of polyphase inclusions in spodumene matite, we can better understand and describe the formation using a dual focused ion beam–scanning electron microscope (FIB–SEM), Can. Mineral., 49, 541–553, 2011. mechanisms of CIs and pegmatites. Anderson, A. J., Clark, A. H., and Gray, S.: The occurrence and origin of zabuyelite (Li2CO3) in spodumene hosted fluid inclusions: implications for the internal evolution of rare-element granitic Data availability. All essential data were presented in Sect. 4 “An- pegmatites, Can. Mineral., 39, 1513–1527, 2001. alytical results” and Table 1. Anthony, J. W., Bideaux, R. A., Bladh, K. W., and Nichols, M. C.: Handbook of Mineralogy, Mineral Data Publishing, Tucson Ari- zona, USA, The Mineralogical Society of America, II, p. 159, Supplement. The supplement related to this article is available on- 1995. line at: https://doi.org/10.5194/ejm-32-67-2020-supplement. Bobos, I., Vieillard, P., Charoy, B., and Noronha, F.: Alteration of spodumene to cookeite and its pressure and temperature stability conditions in Li-bearing aplite–pegmatites from northern Portu- Author contributions. XD analyzed the cookeite samples by using gal, Clay Clay Miner., 55, 295–310, 2007. a Raman spectrometer, an EMP, an FIB-SEM, and a ToF-SIMS and Cerný,ˇ P.: Compositional variation in cookeite, Can. Mineral., 10, also wrote the paper. JL provided the idea of how to identify the Ra- 636–647, 1970. man spectrum of cookeite and explain the formation mechanism of Chou, I-M. and Wang, A.: Application of laser Raman micro- cookeite with distinct Raman spectra in crystal-rich inclusions. IMC analyses to Earth and planetary materials, J. Asian Earth Sci., proposed the significance of cookeite with distinct Raman spectra 145, 309–333, 2017. and gave advice that improved the paper. ZC calculated the IMA Ding, X., Li, J., Li, S., and Wang, X.: Crystallization experiment formula of cookeite according to the EMPA results. SL gave assis- study of zabuyelite using hydrothermal diamond-anvil cell, Acta tance in EMP analysis. Geol. Sin., 90, 873–878, 2016 (in Chinese with English abstract). Downs, R. T.: The RRUFF project: an integrated study of the chem- istry, crystallography, Raman and infrared spectroscopy of minerals, (abs.) the 19th General Meeting of the International Min- eralogical Association, O03-13, 2006.

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Gunter, R.: Tanco Mine Hydrothermal Secondary Minerals Novák, M., Copjaková,ˇ R., Dosbaba, M., Galiová, M. V., Všian- (Online), available at: https://www.mindat.org/article.php/2748/ ský, D., and Stanek,ˇ J.: Two paragenetic types of cookeite from Tanco+Mine+Hydrothermal+Secondary+Minerals+, last access: the Dolní Bory-Hateˇ Pegmatites, Moldanubian Zone, Czech Re- March 2018. public: Proximal and distal alteration productions of Li-bearing Heinrich, E. W.: Economic geology and mineralogy of petalite and sekaninaite, Can. Mineral., 53, 1035–1048, 2015. spodumene pegmatites, Ind. J. Earth Sci., 2, 18–29, 1975. Roedder, E.: Fluid inclusion evidence for immiscibility in magmatic Li, J. and Chou, I-M.: An occurrence of metastable cristobalite in differentiation, Geochim. Cosmochim. Ac., 56, 5–20, 1992. spodumene-hosted crystal-rich inclusions from Jiajika pegmatite Thomas, R.: Determination of water contents of granite melt in- deposit, China, J. Geochem. Explor., 171, 29–36, 2016. clusions by confocal laser Raman microprobe spectroscopy, Am. Li, J. and Chou, I-M.: Homogenization experiments of crystal- Mineral., 85, 868–872, 2000. rich inclusions in spodumene from Jiajika lithium de- Thomas, R. and Davidson, P.: Revisiting complete miscibility be- posit, China, under elevated external pressures in a hy- tween silicate melts and hydrous fluids, and the extreme enrich- drothermal diamond-anvil cell, Geofluids, 2017 9252913, ment of some elements in the supercritical state – Consequences https://doi.org/10.1155/2017/9252913, 2017. for the formation of pegmatites and ore deposits, Ore Geol. Rev., Li, J., Wang, D., Zhang, D., and Fu, X.: Mineralizing mechanism 72, 1088–1101, 2016. and continental geodynamics of typical pegmatite deposits in Thomas, R., Webster, J. D., and Heinrich, W.: Melt inclusions in western Sichuan, China, Atomic Energy Press, Beijing, 187 pp., pegmatite quartz: Complete miscibility between silicate melts 2007 (in Chinese with English abstract). and hydrous fluids at low pressure, Geochim. Cosmochim. Ac., Li, J., Chen, Y., and Wang, D.: The ore-forming mechanism of 139, 394–401, 2000. the Jiajika pegmatite type rare metal deposit in western Sichuan Thomas, R., Davidson, P., and Badanina, E.: A melt and fluid province: evidence from isotope dating, Acta Geol. Sin.-Engl., inclusion assemblage in beryl from pegmatite in the Orlovka 87, 91–101, 2013a. amazonite granite, East Transbaikalia, Russia: Implications for Li, J., Chou, I-M., Yuan, S., and Burruss, R. C.: Observations on pegmatite-forming melt systems, Mineral. Petrol., 96, 129–140, the crystallization of spodumene from aqueous solutions in a hy- 2009. drothermal diamond-anvil cell, Geofluids, 13, 467–474, 2013b. Thomas, R., Davidson, P., and Beurlen, H.: Tantalite-(Mn) from the Li, J., Bassett, W. A., Chou, I. M., Ding, X., Li, S. H., and Wang, Borborema Pegmatite Province, northeastern Brazil: Conditions X. Y.: An improved hydrothermal diamond anvil cell, Rev. Sci. of formation and melt- and fluid-inclusion constraints on experi- Instrum., 87, 1513–1527, 2016. mental studies, Mineral. Petrol., 46, 749–759, 2011a. London, D.: The magmatic–hydrothermal transition in the Tanco Thomas, R., Webster, J. D., and Davidson, P.: Be-daughter minerals rare-element pegmatite: evidence from fluid inclusions and phase in fluid and melt inclusions: Implications for the enrichment of equilibrium experiments, Am. Mineral., 71, 376–395, 1986. Be in granite-pegmatite systems, Contrib. Mineral. Petrol., 161, London, D.: Melt boundary layers and the growth of pegmatitic tex- 483–495, 2011b. tures (abstr.), Can. Mineral., 37, 826–827, 1999. Vidal, O. and Goffé, B.: Cookeite LiAl4(Si3Al)O10(OH)8: Experi- London, D.: Pegmatites, Can. Mineral., Special Publication 10, mental study and thermodynamical analysis of its compatibility Québec, 347 pp., 2008. relations in the Li2O−A12O3−SiO2-H2O system, Contrib. Min- London, D.: Ore-forming processes within granitic pegmatites, Ore eral. Petrol., 108, 72–81, 1991. Geol. Rev., 101, 349–383, 2018. Wagner, W. and Pruss, A.: The IAPWS formulation 1995 for the London, D. and Burt, D. M.: Alteration of spodumene, montebra- thermodynamic properties of ordinary water substance for gen- site, and lithiophilite in pegmatites of the White Picacho district, eral and scientific use, J. Phys. Chem. Ref. Data, 31, 387–535, Arizona, Am. Mineral., 67, 97–113, 1982. 2002.

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